02-13-2012, 04:49 AM
LRRPF52 Wrote:There are more companies who jumped on the bandwagon with 6.8, and in the rush, an unsafe chamber got SAAMI-spec'd somehow, and you have to figure out which one you have or make sure that you DON'T get a SAAMI chamber in 6.8, or it could kaboom on you since it has an 80 degree leade-to-rifling hand-off. This is why the 6.8 SPC II chamber is the one everyone is pointing out to go with, rather than the dangerous one. That makes ammo manufacturers really leary about loading higher-pressure loads, and many 6.8 owners have noticed that their 115gr bullets aren't going the speeds claimed by the makers on the box, or in the original guns that had correct chambers. Many report 200fps less MV, so guess what...they resort to hand-loading, and stick to...small rifle primer brass to handle the pressures..
The reason for the pressure spikes was not the chamber so much as bores with cross-sectional areas below SAAMI min. The shorter lead in the SAAMI chamber, by itself, it only a 1000 psi difference. That works out to about 20 fps. Rifle factories shoot SAAMI proof rounds in SAAMI chambered rifles, and they are 72,000+ PSI.